【求助】请高手帮我看看我的电子衍射标对了吗。非常感谢

问一个问题，你标定的时候为什么不选最小的平移周期呢？如图。

非常感谢您！我是根据一篇文献标的。但是不是同一种物质 （Bi2Te3)，只是都是六方的晶体结构，并且衍射图非常象。另外我也按照论坛里说的方法，量距离，可是量出来的结果跟XRD卡片相差很大，不知道该如何确定。还请高手指点迷津。

如果是六方结构，这有可能是[001]方向的衍射花样。你测量的d值与卡片差多大？

我量的d(A)=3.862，而XRD中最大的d(A)=3.678。我觉得量距离本身就存在较大的误差。特别是HRTEM中，我觉得用尺很难量出较准确的值。不知道大家是如何量出来的。

实验、相机常数的确定以及测量过程中都会产生误差，XRD的结果是3.678，TEM的结果是3.862，可以接受，标定电子衍射花样关键是看晶面之间的夹角。

非常感谢版主的热心帮助！

From your xrd results, the sample seems to be ploycrystal not single crystal. So why don't you take the SAED photo(from low mag BF)?
I have two more questions and one suggestion.
1. How did you calculate the interplanar d spacing for each plane?
2. Why there is no scale bar in the ED pattern or any information about your operation conditions? If you know these informations, then you can calculated d values by camera constant method.
3. It is dangerous to index the pattern just by inspection with similar patterns.
Good luck

lingling1149 发表:

此物质是六方相的LaF3,PDF 卡片为32-0483。刚开始涉及这方面，恳请各位高手指点。

首先非常感谢你的建议。1. How did you calculate the interplanar d spacing for each plane?我是用卡尺直接在底片上量的。
2. Why there is no scale bar in the ED pattern or any information about your operation conditions? If you know these informations, then you can calculated d values by camera constant method.衍射底片本来就没有标尺呀，只是用特定型号的电镜就有固定的相机常数。我们用的是2010，200Kv,所以 相机常数（Lλ）中λ=0.00251nm。
另外我想请教一下：通过XRD如何来判断是单晶还是多晶.非常感谢！

Generally speaking, if your samples are ploycrystal, there will be all diffracted peaks allowed by the structure factors of that material. If the sample is single crystal, the peaks will not be shown like those of JCPDS card. There are only some planes can be observed along the orientation of the crystalline. Say, the common planes alone C orientation are (00L)s.